Oxidation of antibiotics with KMnO₄: Drinking water treatment and removal of antibiotic activity

Several recent reports have documented the presence of antibiotics in drinking water sources, the result of incomplete treatment of waste streams originating from municipal sources and livestock operations. Although these compounds are detected at sub-therapeutic levels, their presence raises concerns about ecotoxicological and public health risks associated with long-term exposure. As a result, there is also growing interest in the fate of antibiotics during drinking water treatment processes. Potassium permanganate (KMnO ₄) is used by a number of utilities to address a range of issues (e.g., dissolved Mn, T&O), but little is known about the effectiveness of KMnO₄ for oxidizing antibiotics or the effect of treatment on antibiotic potency of the treated water. This contribution reports for the first time on treatment of commonly detected antibiotics (trimethoprim, lincomysin, ciprofloxacin, sulfamethoxazole, sulfamethizole, and chlortetracycline) with KMnO₄. Kinetic studies demonstrate that KMnO₄ is a selective oxidant, exhibiting apparent second-order rate constants with the target antibiotics at pH 7 ranging from <0.03 to 110 M^-1 s ^-1. Reaction rates are highly dependent on pH, and measured kinetic trends can be modeled by accounting for changes in acid/base speciation of the target antibiotics. Kinetic model predictions also agree closely with measurements of antibiotic treatment in drinking water utility source waters of variable composition. Bioassay experiments show that oxidation products and intermediates possess negligible antibacterial activity in comparison with the parent drugs. 2009